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ARRL Propagation Bulletin ARLP011 (2012)

ARLP011 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 11  ARLP011
From Tad Cook, K7RA
Seattle, WA  March 16, 2012
To all radio amateurs 

ARLP011 Propagation de K7RA

Average daily sunspot numbers over the past reporting week (March
8-14) were 88.3, a rise of nearly 19 points.  Average daily solar
flux rose over 12 points to 134.2.

Four new sunspots emerged, the first was sunspot group 1432 on March
9 (misidentified as 1421 in yesterday's ARRL Letter), which began
with a relative area of 90, and in the following days went to 80,
50, 80, 70, 60 and 100. Two sunspot groups, numbered 1433 and 1434
appeared on March 11, with a combined relative size (in millionths
of a solar hemisphere) of 240, then 130, 140, 150 and 150.

Finally on March 15, a new sunspot group 1435 emerged, with a
relative size of 30. The daily sunspot number on this day rose to

The sunspot number peaked on March 11 at 103, and the solar flux on
March 10 at 148.9 and again on March 13 at 140.7.  The outlook for
the next few days has solar flux at 110 on March 16, 105 on March
17-21, 100 on March 22, 105 on March 23-27, 110, 115 and 125 on
March 28-30, and 130 on March 31 through April 5.

There was a great deal of geomagnetic activity on March 9 with a
planetary A index at 68, and again on March 12 with a planetary A
index of 28. An M-class x-ray flare occurred on March 15 at 0752
UTC, and if you catch it soon enough, you can see the resulting
x-ray flux on the GOES monitor at,

The predicted planetary A index for March 16-17 are 18 and 10, then
5 for March 18-27, 10 on March 28, 8 on March 29-31, 5 on April 1-2,
8 on April 3-4 and 5 on April 5-9.

The Vernal Equinox will occur at 0514 UTC on March 20. The shift to
Spring in the Northern Hemisphere and Autumn in the Southern
Hemisphere generally signals favorable conditions for HF

Thanks to Howard Lester, N7SO, who sent in a photo of a backyard
telescope in Brooklyn, New York owned by Alan Friedman and operated
among city lights:

Howard also sent this solar image from March 11 using the same
telescope, with appropriate filters, of course:

A detail of region 1429:

NASA posted a nice image plus a video of sunspot region 1429. See it

Scott Woelm, WX0V of Fridley, Minnesota wrote: "Bob Conzemius,
KB0ZXT, of Grand Rapids, Minnesota has some rather spectacular
time-lapse video of aurora displays.  These can be accessed on his
youtube site at"

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at For an explanation of the
numbers used in this bulletin, see An archive of past
propagation bulletins is at Find more good
information and tutorials on propagation at

Monthly propagation charts between four USA regions and twelve
overseas locations are at

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for March 8 through 14 were 86, 96, 89, 103, 89, 80,
and 75, with a mean of 88.3. 10.7 cm flux was 139.5, 145.5, 148.9,
131.2, 114.9, 140.7, and 118.8, with a mean of 134.2. Estimated
planetary A indices were 24, 68, 18, 8, 28, 10, and 8, with a mean
of 23.4. Estimated mid-latitude A indices were 21, 57, 17, 10, 28,
10, and 6, with a mean of 21.3.


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